III/V-semiconductor

ABSTRACT

The invention relates to a monolithic integrated semiconductor structure comprising a carrier layer on the basis of doped Si or doped GaP and a III/V semiconductor disposed thereupon and having the composition Ga x In y N a As b P c Sb d , wherein x=70-100 mole-%, y=0-30 mole-%, a=0.5-15 mole-%, b=67.5-99.5 mole-%, c=0-32.0 mole-% and d=0-15 mole-%, wherein the total of x and y is always 100 mole-%, wherein the total of a, b, c and d is always 100 mole-%, and wherein the ratio of the totals of x and y on the one hand and of a to d on the other hand is substantially 1:1, to methods for the production thereof, new semiconductors, the use thereof for the production of luminescence diodes and laser diodes or also modulator and detector structures, which are monolithically integrated in integrated circuits on the basis of the Si or GaP technology.

FIELD OF THE INVENTION

The invention relates to a new III/V semiconductor, a semiconductorlayer consisting of such a semiconductor, a monolithically integratedsemiconductor structure comprising such a semiconductor layer, the usesof such a semiconductor or of such a semiconductor layer, and a methodfor the production of such a semiconductor layer.

BACKGROUND OF THE INVENTION AND PRIOR ART

In the field of computer technology, there is a continuously growingdemand for higher processing and signal conduction capacities inconjunction with a high reliability and flexibility. In the past, thechip technology has made a rapid progress with regard to integrationdensity and working speeds or cycle frequencies. With this trend furtheradvancing, problems are coming up for the connection of fast chips.Critical aspects in conjunction with high-speed connections arereliability, cost, on-chip driver size and performance, crosstalk,signal distortions and lack of flexibility in the chip design.Connections between chips by using optoelectronic components and opticalwaveguides are a solution for many connection problems. Opticalconnections have an extremely high bandwidth and are comparativelyinsensitive against crosstalk and other interferences. By using theseproperties of optical connections, it may become possible to connecthigh-speed chips with each other by optical channels and to achieve aconsiderable improvement with regard to connection density, currentconsumption, interferences and crosstalk.

Usually high-integrated circuits are based on the Si technology.Silicium is however an indirect semiconductor, and the production ofefficient optoelectronic components using the Si technology isconsequently hardly possible. Efficient optoelectronic components canhowever be produced by using the technology of the III/V semiconductors,for instance the GaAs technology, since these semiconductors are oftendirect semiconductors consequently emitting and absorbing light with ahigh efficiency.

For producing integrated circuits, commonly the epitaxial process isemployed. If now contacts between layers on the basis of the Sitechnology and layers on the basis of the technology of the III/Vsemiconductor are to be made, it is problematic that the latticeconstants of the respective materials are different (this also appliesto GaP substrates instead of Si substrates). This has as a consequencethat during the epitaxial growth of III/V semiconductors on Si (or GaP)substrates, dislocations are created. Such dislocations however disturbthe function of the complete semiconductor structure to a substantialdegree, the more since the functional layer thicknesses are today in theorder of atomic dimensions. In the case of high layer thicknesses, thedifference of the lattice constants even leads to bends of thesubstrate. The reason for this is basically that with high depositiontemperatures an epitaxial growth of III/V semiconductors takes place onSi or GaP semiconductors, however the generation of dislocations beginsalready at less high deposition temperatures. If then the semiconductorstructure cools down to ambient temperature, the differences of thelattice constants caused by the different thermal expansion coefficientswill lead to the above stresses and dislocations.

For eliminating the above problems, various approaches exist. In thedocument EP 0380815 B1 there is described that GaAs layers can bedeposited on a Si substrate and form defined microcracks atpredetermined positions, thus dislocations of the Si substrate beingavoided, at least however reduced. This technology is however notsuitable for high-integrated circuits because of the lackingcontrollability of microcracks in atomic scales.

The document EP 0297483 describes a hybrid integrated semiconductorstructure, wherein on a Si substrate an integrated circuit on the basisof the Si technology is applied. Further, an optically active element inGaAs technology is provided on the Si substrate. An electricalconnection between the integrated circuit and the optically activeelement is however not established by a direct contact or by the Sisubstrate, but rather by an electrical wire connection. This technology,too, is not suitable for applications in high-integrated circuits.

From the document DE 10355357 it is known, for layer structures withoptically active elements on the basis of III/V semiconductors, tocompensate dislocations caused by lattice constants for instance byadaptation layers subjected to tensile stress. By the insofar knownmeasures, a modeling of electronic properties is also possible, and thusemission wavelengths not accessible up to now become accessible.

From the document US 2004/0135136 A1, a multitude of different III/Vsemiconductors are known in the art, and they are always layers, whichare not suitable for application on a Si substrate. Correspondingconsiderations apply to the documents EP 1257026 A2, U.S. Pat. No.6,233,264 B1, US 2004/0084667 A2, Merz et al., IEE Proc.-Optoelectron.151(5):346-351 (2004), U.S. Pat. No. 6,072,196, EP 1553670 A2, U.S. Pat.No. 5,825,796, Ishizuka et al., Journal of Crystal Growth 272:760-764(2004) and US 2004/0161009 A1.

In the document EP 0896406 A2 there are described layers of opticallyactive III/V semiconductors on GaP or Si substrates (and others), andthese layers contain exclusively In as the III component. In fact, suchlayers are only suitable for InP substrates and form undesirably manydislocations and faults on Si or GaP substrates. The document U.S. Pat.No. 5,937,274 describes in a very general manner different layers ondifferent substrates.

As a result, there continues being a need in particular for the field ofhigh-integrated circuits to connect subassemblies or layer sequences onthe basis of the Si technology and on the basis of the III/Vsemiconductor monolithically with each other.

TECHNICAL OBJECT OF THE INVENTION

It is a technical object of the invention to propose means for providingoptically active elements on the basis of the III/V semiconductors onsubstrates of the Si technology or GaP technology, wherein theconduction of electrical signals of the Si based or GaP-basedsubassemblies to and from the optically active elements is integrallyformed, i.e. by contact of layers, and that practically free fromdislocations forming nonradiative recombination centers in the III/Vsemiconductor or at the border face thereof to the layer underneath. Itis further a technical object of the invention to propose stableluminescence and laser components on Si substrates or GaP substrates,which are directly contacted, i.e. by layer contact. It is anothertechnical object of the invention to provide a monolithically integratedsemiconductor structure, which emits directly, i.e. without wireboundconnection lines, data currents from a Si-technology based processorcircuitry as an optical signal. Further, it is an object of theinvention to propose a monolithically integrated semiconductorstructure, by means of which emitted optical signals can also bemodulated and/or detected.

BASICS OF THE INVENTION AND EMBODIMENTS

For achieving this technical object, the invention teachesmonolithically integrated semiconductor structures according to claim 1with Si or GaP substrates and a III/V semiconductor having thecomposition Ga_(x)In_(y)N_(a)As_(b)P_(c)Sb_(d), wherein x=70-100 mole-%,y=0-30 mole-%, a=0.5-15 mole-%, b=67.5-99.5 mole-%, c=0-32.0 mole-% andd=0-15 mole-%, wherein the total of x and y is always 100 mole-%,wherein the total of a, b, c and d is always 100 mole-%, and wherein theratio of the totals of x and y on the one hand and of a to d on theother hand is substantially 1:1. Preferably, y=1-30 mole-%, and c=1-32.0mole-%, and such a semiconductor per se.

In the case of a P-free system, In and/or Sb should be comprised, sincethese elements minimize, like P, the local distortion fields caused bythe N-incorporation.

III/V semiconductors having the following compositions are particularlypreferred:

-   a) x=70-100 mole-%, y=0-30 mole-%, a=0.5-10 mole-%, b=70-98.5    mole-%, c=1-29.5 mole-%, or-   b) x=85-99 mole-%, y=1-15 mole-%, a=0.5-10 mole-%, b=70-98.5 mole-%,    c=1-29.5 mole-%, or-   c) x=85-99 mole-%, y=1-15 mole-%, a=0.5-10 mole-%, b=70-98.5 mole-%,    c=0-32 mole-% and d=1-10 mole-%.

In particular, x=>70-100 mole-%, a=>1.3 or >1.7 mole-% (optionally inconnection with y>0 or 1 mole-%), c=0-32 mole-% and/or b=60-99.5 mole-%.Preferred is also c= or between 4-8 mole-%. Preferred is also a=4 or5.5-11 mole-%.

The semiconductor class according to the invention of the mixed crystalsystem GaInNAsPSb is characterized, on the one hand, by that because ofthe composition, presumably of the addition of nitrogen and/phosphorus,layer sequences adapted to the lattice or compressively stressed can beproduced on GaP and/or Si substrates, without causing dislocations. Onthe other hand, beginning from a nitrogen concentration of >0.5 mole-%in conjunction with the phosphorus content, an interaction of theelectronic levels caused by the incorporation of nitrogen with theconduction band states of the nitrogen-free mixed crystal system at theΓ point will occur, which will lead to an effective red shift of thefundamental energy gap at the Γ point and thus strengthen the characteras a direct semiconductor of the GaInNAsPSb material system. Forinstance, for a=1-10 mole-%, b=60-95 mole-% and c=2-15 mole-%,preferably a=3-5 mole-%, b=85-95 mole-% and c=4-8 mole-%, there willresult a fundamental energy gap of distinctly less than 1.8 eV, evendown to 1.4 eV and smaller. This makes clear the drastic influence ofthe energy gap by the composition of this semiconductor system accordingto the invention.

In detail, the invention relates to a monolithically integratedsemiconductor structure comprising the following layer structure:

A) a carrier layer on the basis of doped or undoped Si or GaP,

B) as an option, a first current-conducting layer composed of doped Si,doped GaP or doped (AlGa)P,

C) as an option, a first adaptation layer, and

D) an optically active element comprising a semiconductor layeraccording to the invention.

To the layer D), the below layers may follow: E) optionally a secondadaptation layer and F) a second current-conducting layer composed ofdoped Si or doped GaP or doped (AlGa)P. In case of the (AlGa)P, theshare of Al may be 20-100 mole-%, and the total of the shares of Al andGa is always 100 mole-%. The layer B) may be p or n-doped. In case thatthe layer F) is present, the layer F) may be p-doped, if layer B) isn-doped, and vice versa.

Normally, the optical element will have a layer structure(D1-D2-D3)_(n), wherein the layer D2 is a quantum well layer of asemiconductor according to the invention, wherein the layers D1 and D3are barrier layers, and wherein n=1-15. By such an optically activeelement, luminescence diodes as well as laser diodes can be built up.Following one of the terminal layers D1 or D3, a barrier layer D4 may beprovided. It may be recommended that the barrier layers aresemiconductors having the composition Ga_(p)—In_(q)N_(r)P_(s)As_(t),wherein p=85-100 mole-%, q=0-15 mole-%, r=0-15 mole-%, s=60-100 mole-%and t=0-40 mole-%, wherein the total of p and q is always 100 mole-%,wherein the total of r, s and t is always 100 mole-%, and wherein theratio of the totals of p and q on the one hand and of r to t on theother hand is substantially 1:1, and wherein the barrier layer has alayer thickness of preferably 5-50 nm. Preferred ranges are: p=90-100mole-%, q=0-10 mole-%, r=0-10 mole-%, s=70-100 mole-% and t=0-30 mole-%.For the layer thickness, a range of 2-20 nm is preferred. An adaptationlayer may be a semiconductor having the compositionGa_(p)In_(q)N_(r)P_(s)As_(t), wherein p=90-100 mole-%, q=0-10 mole-%,r=0-10 mole-%, s=70-100 mole-% and t=0-30 mole-%, wherein the total of pand q is always 100 mole-%, wherein the total of r, s and t is always100 mole-%, and wherein the ratio of the totals of p and q on the onehand and of r to t on the other hand is substantially 1:1, and whereinthe adaptation layer has a layer thickness of preferably 50-500 nm.

In the monolithically integrated semiconductor structure according tothe invention, a current-conducting layer and/or barrier layer disposedbetween the carrier layer and the optically active element may be at thesame time an adaptation layer.

Underneath and/or above the optically active element, at least oneoptical waveguide layer may be provided, which is optically coupled tothe optically active element. In this way, data currents can be guidedas optical signals from the emitting optically active element to anoptical receiver at a different place on the carrier. It is understoodthat other elements may additionally or alternatively be used forconducting optical signals, such as fibers or the like.

A luminescence diode or also a vertically emitting laser diode may beproduced by that between the layers A) and D) and/or outside the layerF), there is provided at least one periodic reflection structure.

Preferably, the optically active element has a fundamental emissionwavelength in the range of 700-1,100 nm.

The invention further relates to the use of a semiconductor according tothe invention or a semiconductor layer according to the invention forthe production of a luminescence diode (LED), a VCSEL (vertical cavitysurface emitting laser) laser diode or a VECSEL (vertical externalcavity surface emitting laser) laser diode and a modulator or a detectorstructure.

Finally, the invention relates to a method for the production of asemiconductor layer according to the invention comprising the followingsteps: a substrate on the basis of doped or undoped Si or GaP is broughtinto a MOVPE (metal-organic vapor phase epitaxy) apparatus, optionally asurface of the substrate is provided in at least one epitaxial coatingstep first with respectively at least one adaptation layer, one barrierlayer, one current-conducting layer, one waveguide layer and/or onereflection structure, a carrier gas is loaded with educts in definedconcentrations, the loaded carrier gas is conducted over the surface ofthe substrate heated to a temperature in the range of 300° C. to 700° C.or on the surface of the uppermost layer on the substrate for a definedduration of exposure, and the total concentration of the educts and theduration of exposure are adjusted to each other such that thesemiconductor layer is epitaxially formed with a given layer thicknesson the surface of the substrate or on the surface of the uppermost layeron the substrate.

Preferably, the following educts are used for the MOVPE technology:C1-C5 trialkylgallium, in particular triethylgallium (Ga(C₂H₅)₃) and/ortrimethylgallium (Ga(CH₃)₃), as a Ga educt, C1-C5 trialkylindium, inparticular trimethylindium (In(CH₃)₃), as an In educt, ammonia (NH₃),mono(C1-C8)alkylhydrazine, in particular tertiarybutylhydrazine(t-(C₄H₉)—NH—NH₂), and/or 1,1-di(C1-C5)alkylhydrazine, in particular1,1-di-methylhydrazine ((CH₃)₂—N—NH₂), as an N educt, arsine (AsH₃)and/or C1-C5 alkylarsine, in particular tertiarybutylarsine(t-(C₄H₉)—AsH₂), as an As educt, phosphine (PH₃) and/or C1-C5alkylphosphine, in particular tertiarybutylphosphine (t-(C₄H₉)—PH₂), asa P educt, and C1-C5 trialkylantimony, in particular trimethylantimony((CH₃)₃Sb) and/or triethylantimony ((C₂H₅)₃Sb), as an Sb educt, whereinthe C3-C5 alkyl groups may be linear or branched.

Preferably, the educts are employed in the following molar ratios: Aseduct/group III educts 5-300, P educt/group-III educts 0-500, N educt/Aseduct 0.1-10, optionally Sb educt/As educt 0-1, wherein the surfacetemperature of the substrate is adjusted to the range from 500° C. to630° C., wherein the total pressure of carrier gas and educts isadjusted to the range from 10 to 1,000 hPa or to 200 hPa, wherein theratio of the total of the partial pressure of all educts to the partialpressure of the carrier gas is between 0.005 and 0.1, and wherein thedeposition rate is 0.1 to 10 μm/h. In particular the following ratiosmay be employed: As educt/group III educts 10-100, for instance 10-30, Peduct/group III educts 1-100, for instance 1-10, N educt/As educt 1-10,for instance 3-8. The surface temperature may preferably be in the rangefrom 500° C. to 650° C., in particular 550° C. to 600° C. The totalpressure of carrier gas and educts may be in the range from 20 to 100hPa. The ratio of the partial pressure of all educts to the partialpressure of the carrier gas may be in the range from 0.01 to 0.05. Thedeposition rate may be between 0.1 and 5 μm/h, in particular 0.5 and 3μm/h.

In principle, the precise concentrations of the educts depend on thethermal decomposition properties of the respective educts in the MOVPEprocess. The growth speed of the layer is determined by theconcentrations of the group III educts. On the basis of variousdecomposition properties of the Ga and if applicable In educts, known tothe man skilled in the art, depending on the selected depositiontemperature (surface temperature of the substrate), suitable eductconcentrations are adjusted, which will lead to the desired group IIIconcentrations of the respective elements in the semiconductor layeraccording to the invention. Because of the known temperature-dependentincongruent vaporization of the group V educts or species of the growthsurface of the III/V semiconductors, the respective group V eductconcentrations in the MOVPE deposition should carefully be adjusted tothe desired concentrations in the semiconductor layer according to theinvention as a function of the selected deposition temperature in theexcess. This is easily achievable for the man skilled in the art. Forhigher deposition temperatures or educts that cannot easily bedecomposed, if applicable, higher V/III ratios, but also higher N/Asratios than mentioned above have to be selected. For lower depositiontemperatures, correspondingly the reversed behavior applies.

Alternatively to MOVPE, of course other epitaxial methods can also beemployed, such as MBE (molecular beam epitaxy), also under inclusion ofgas sources in particular for the group V components (gas source MBE,GS-MBE), CBE (chemical beam epitaxy) or also MOMBE (metal-organicmolecular beam epitaxy). These methods can be carried out by means ofthe usual and per se known epitaxy apparatuses, and the respectivelysuitable and per se known educts and sources have to be employed. Therespective conditions can easily be adjusted by the man skilled in theart.

A method for the production of a semiconductor structure according tothe invention is described in the claims 22 to 33.

DEFINITIONS

A direct semiconductor is a semiconductor, where in the band structurethe valence band maximum and the conduction band minimum are locatedopposite to each other at the same crystal pulse vector. In contrastthereto, for an indirect semiconductor, the valence band maximum and theconduction band minimum are not located opposite to each other at thesame crystal pulse vector, but are located at different crystal pulsevectors.

A monolithic semiconductor structure is a structure, wherein an electriccontact of different functional semiconductor sections occurs by(preferably epitaxial) layers immediately connected with each other. Incontrast thereto, in a hybrid semiconductor structure, an electricalcontact of different functional semiconductor sections is achieved byauxiliary connections, such as for instance wire connections.

In an n-doped semiconductor, the electrical conduction is achieved byelectrons because of donor atoms having extra valence electrons. For then-doping of silicon, there can for instance be used nitrogen,phosphorus, arsenic and antimony. For the n-doping of GaP or (AlGa)Psemiconductors, for instance silicon and tellurium can be used. In ap-doped semiconductor, the electrical conduction occurs by holes becauseof the incorporation of acceptor atoms. Acceptors for silicon are boron,aluminum, gallium and indium. For GaP or (AlGa)P can be used forinstance magnesium, zinc or carbon as acceptors.

A semiconductor is typically undoped, if the concentration of donor oracceptor atoms is below 10⁵ cm⁻³. Doped semiconductors usually haveconcentrations above 10¹⁵ cm⁻³.

A current-conducting layer consists of a semiconductor doped to such anextent that a conductivity being sufficient for providing a definedelectrical power is given.

III/V semiconductors according to the invention are typicallycompressively stressed. For the purpose of the lattice adaptation andmodeling of the band structure, barrier layers are provided, which maybe tensile-stressed. Thereby, a compensation of the stress of the III/Vsemiconductor is achieved.

An optically active element according to the invention transforms energyinto light radiation and emits the latter, modulates the light radiationand/or absorbs light radiation and transforms it into an electricalsignal. For laser diodes, the number of layer periods n is typically1-5. For luminescence diodes, n may however be up to 15. For modulatorsor detector structures, n may be substantially higher and have values ofup to 50 and more.

An adaptation layer serves for the compensation of stresses of asemiconductor layer or a semiconductor structure according to theinvention on the basis of III/V semiconductors on Si or GaP substrates.Adaptation layers do not contribute to light emission.

A quantum well layer is also called a quantum film. By the two-sidecontact with a barrier layer, the movements of the charge carriers areconfined, and the charge carriers are in the case of epitaxial layers ina one-dimensional inclusion (movements mainly in two spatialdimensions). Optically active elements having the layer structureaccording to the invention are also called multiple quantum well (MQW)structures. By epitaxial stresses between the quantum well layers andthe barrier layers, the electronic properties with regard to thefundamental band gap can be influenced.

Optical waveguide layers are widely known from prior art. As an exampleonly, reference is made to the document “Semiconductor Optoelectronics:Physics and Technology”, J. Singh, McGraw-Hill Inc., New York (1995).

Periodic reflection structures are dielectric and/or epitaxial (λ/4)multi-layer mirrors. They are so-called distributed Bragg reflectors(DBR), reflecting the light emitted by the optically active element andrepresenting thus the high-reflective end mirror in the laser resonator.With regard thereto, reference is made to the document “Vertical-cavitySurface-emitting Lasers: Design, Fabrication, Characterization andApplication”, Eds.: C. Wilmsen et al., Cambridge University Press,Cambridge (1999). Such periodic reflection structures may also be p orn-doped for the purpose of current conduction. Then these periodicreflection structures accept at the same time the function of acurrent-conducting layer.

III/V semiconductors according to the invention are typically metastableat room temperature or at operating temperature. This means that becauseof the thermodynamics of the situation at the respective temperature,there should not exist a stable, homogeneous phase, but that a decayinto at least two different phases should occur. This decay is howeverkinetically inhibited. For overcoming the kinetic inhibition, a hightemperature would be required to act, and for this reason suchmetastable phases can only be epitaxially deposited at comparatively lowsubstrate temperatures, typically below 700° C. After the deposition atreduced temperatures, an annealing step of the semiconductor layeraccording to the invention may be employed in the temperature range oftypically 700° C. to 850° C. for the reduction of nonradiativerecombination centers. There can be performed equilibrium annealingsteps, for instance immediately in a MOVPE reactor, as well asnon-equilibrium methods, such as rapid thermal annealing (RTA). Therespective annealing temperatures are to be selected such that no decayinto different phases is observed.

The carrier layer used according to the invention is typically a GaP orSi single crystal. It is understood that the surface of such a singlecrystal may be purified in a conventional manner and prepared for theepitaxial deposition. In this context, reference is made to the documentA. Ishizaka et al., Electrochem. Soc. 33:666 (1986).

The term “substantially 1:1” comprises the range of 0.8:1.2-1.2:0.8, inparticular 0.9:1.1-1.1:0.9, preferably 0.95:1.05-1.05:0.95, and ofcourse also exactly 1:1.

EMBODIMENTS OF THE INVENTION EXAMPLE 1 Production of a SemiconductorLayer According to the Invention

After the usual pretreatment, a Si wafer (manufacturer: Wacker, VirginiaSemiconductor) is placed in a MOVPE apparatus (type AIX200-GFR,manufacturer Aixtron). First, epitaxial layers are deposited in aconventional way on the Si wafer, as described in more detail in thefollowing Examples. On the thus obtained surface, then a layer of theIII/V semiconductor according to the invention is deposited. For thispurpose, an inert gas flow (H₂) is loaded with the various educts. Thefollowing educts are used: trimethylgallium or triethylgallium,trialkylindium (as far as applicable), 1,1-dimethylhydrazine,tertiarybutylarsine, tertiarybutylphosphine and trimethylantimony (asfar as applicable). All these educts are for instance available fromAkzo Nobel HPMO.

For the production of a semiconductor layer according to the inventionhaving an exemplary composition Ga(N_(0.037)As_(0.883)P_(0.08)), thefollowing conditions were selected with a total reactor pressure of 50hPa: partial pressures TEGa (triethylgallium) 0.007 hPa, TBAs(tertiarybutylarsine) 0.142 hPa, TBP (tertiarybutylphosphine) 0.035 hPaand UDMHy (dimethylhydrazine) 0.85 hPa. Therefrom result the followingratios: ratio As/Ga 20, ratio P/Ga 5 and ratio N/As 6.

The loaded H₂ carrier gas having a total pressure of 50 hPa is thenconducted for 22 s over the surface of the coated substrate heated to575° C. A layer according to the invention having a thickness of 7.0 nmis obtained. After expiration of the exposure period for thesemiconductor layer according to the invention, the MOVPE system isadjusted to the deposition conditions of the respective barrier oradaptation layer.

EXAMPLE 2 Production of an Optically Active Element

In the MOVPE apparatus of Example 1, first the layers described in thefollowing examples are epitaxially grown on a Si wafer in a conventionalmanner. Thereafter, alternatingly a barrier layer and a quantum welllayer each are deposited, and the deposition of a barrier layerrepresents the completion. This periodic layer structure comprises intotal 5 quantum well layers. As the quantum well layer, a layeraccording to Example 1 is used. All quantum well layers have the samecomposition. As the barrier layer, GaP is used. All barrier layers havethe same composition. The quantum well layers have thicknesses between 2and 20 nm each. The barrier layers have thicknesses between 5 and 500nm.

EXAMPLE 3 Monolithic Integrated Semiconductor Structure According to theInvention

A monolithic integrated semiconductor structure according to theinvention is shown in FIG. 1. For the production, the layers B1) to F2)are subsequently epitaxially grown on a Si wafer A. The layer B1) isp-doped GaP. Zinc or magnesium is used as doping element. The dopingconcentration is typically 1·10¹⁸ cm⁻³. The layer thickness of the layerB1) is 5-300 nm. The layer B1) is a contact layer, which is also currentconducting. Thereafter, the layer B2) is produced, which is formed ofp-doped (AlGa)P. Doping is made with zinc or magnesium in a dopingconcentration of typically 1·10¹⁸ cm⁻³. The aluminum concentration ismore than 15 mole-%, referred to the total amount of group III elements.A typical value is in the range of 15-45 mole-%. Alternatively, p-doped(AlGa)(NP) can also be used, and with regard to doping and aluminumcontent the above applies. The share of nitrogen referred to the totalamount of group V elements, is 0-4 mole-%. The layer thickness isbetween 500 and 1,500 nm. The layer B2) is a waveguide layer, which actsat the same time as a current-conducting layer. The layer C) disposedthereupon is composed of undoped GaP. The layer thickness is 50-100 nm.It is a separate confinement heterostructure similar to a barrier layer.Further, the layer C) acts as an adaptation layer. For bettervisibility, the optically active element D) disposed thereupon is shownas a single layer. In fact, the layer D) is a layer structure accordingto Example 2. The layer E) corresponds to the layer C). Alternatively,both layers can also be adapted as Ga(NP), (GaIn)(NP) or (GaIn)(NaSP)layers. The nitrogen share referred to the group V elements may be 0-10mole-%. In the case of the latter layer, the share of In referred to thetotal amount of group III elements may be 0-15 mole-%. The layer F1)corresponds to the layer B2), and the layer F2) corresponds to the layerB1), with the difference that the layers F1) and F2) are n-doped. As thedoping element, tellurium with a doping concentration of typically2·10¹⁸ cm⁻³ is employed. The layer thicknesses of the layers E), F1) andF2) correspond to the layer thicknesses of the layers C), B2) and B1)(in a reflection-symmetric order with regard to the optically activeelement).

For improving the degree of output coupling, for luminescence diodes asoptically active elements, in addition (AlGa)/P/(AlGa)/P periodicreflection structures (DBR structures) having different aluminumcontents can be incorporated in the current-conducting layer locatedunder the optically active element. The aluminum share of successivelayers is different and is, referred to the total amount of group IIIelements, 0-60 mole-% or 40-100 mole-%, resp. Alternatively, (AlGa)(NP)individual layers may also be used for the compensation of stress ofthese DBR structures, and the Al contents are to be selected as above,and the N contents from 0-4 mole-%, referred to the total amount ofgroup V elements.

For surface emitting laser diodes (VCSEL) as optically active elements,the optically active element is enclosed from below as well as fromabove by a reflection structure of the above type. For current supply,either these two DBR mirror structures may be n-doped or p-doped, oradditionally so-called intra cavity current contacts are introduced inthe overall structure, said contacts permitting to produce the two DBRmirrors in an undoped condition.

EXAMPLE 4 Fundamental Energy Gap of a Semiconductor According to theInvention

A semiconductor layer produced according to Example 1 with 4 mole-%nitrogen, 90 mole-% arsenic and 6 mole-% phosphorus, referred to thetotal amount of group V elements, was investigated by means of thephotoluminescence excitation spectroscopy. The result is shown in FIG.2. The fundamental energy gap is approx. 1.4 eV. This value is clearlylower than the value of 1.8 eV modeled without the nitrogen interactionand shows the drastic influence of the energy gap by the incorporationof nitrogen in coordination with the further shares of other componentsin the semiconductor system according to the invention.

EXAMPLE 5 Dislocation-Free Structure of Optically Active ElementsAccording to the Invention

An optically active element produced according to Example 2 wasinvestigated by means of the high-resolution x-ray diffraction (HR-XRD)and of the transmission electron microscopy (TEM).

FIG. 3 shows an experimental HR-XRD profile (FIG. 3 top) in comparisonwith a theoretical profile according to the dynamic x-ray diffractiontheory (FIG. 3 bottom). The observed sharpness of the individualdiffraction reflexes and the nearly perfect match of the experimentaland theoretical diffraction profiles confirm the outstanding structurallayer quality over a large area without generation of dislocations.

FIG. 4 shows a TEM dark field image. There can be seen pentanary layersaccording to the invention as dark layers. The lighter layers are Ga(NP)barrier layers. All three layers are clearly resolved, and there cannotbe seen any large-area defects in the crystalline structure. In thehigh-resolution TEM image of FIG. 5, there are nearly atomically abruptborder faces at the transition of the (dark) pentanary layer accordingto the invention to the barrier layer, said border faces being free fromdislocations and the like.

EXAMPLE 6 Semiconductors with a Particularly Low Fundamental Energy Gap

Different semiconductor layers produced analogously to Example, saidlayers however containing nitrogen in the range of 5.5 to 11 mole-% (asalways, referred to the total amount of group V elements), show in theinvestigation by means of photoluminescence spectroscopy at 20° C. afundamental, direct energy gap of less than 1.2 eV, even less than 1.1eV, which is below the energy gap of silicon (1.124 eV). Semiconductorlayers having an energy gap below that of silicon in particular for theproduction of luminescence and laser diodes, which are integrated withSi/SiO₂-based waveguide structures. In particular for these emissionenergies, there will namely be no absorption and thus attenuation of thelight signal in the waveguide structure.

1. A monolithic integrated semiconductor structure comprising thefollowing layer structure: A) a carrier layer on the basis of doped orundoped Si or GaP, B) as an option, a first current-conducting layercomposed of doped Si, doped GaP or doped (AlGa) P, C) as an option, afirst adaptation layer, and D) an optically active element comprising asemiconductor layer formed from a III/V semiconductor having thecomposition Ga_(x)In_(y)N_(a)As_(b)P_(c)Sb_(d), wherein x=70-100 mole-%,y=0-30 mole-%, a=0.5-15 mole-%, b=67.5-99.5 mole-%, c=0-39.5 mole-% andd=0-15 mole-%, wherein the total of x and y is always 100 mole-%,wherein the total of a, b, c and d is always 100 mole-%, and wherein theratio of the totals of x and y on the one hand and of a to d on theother hand is substantially 1:1.
 2. A semiconductor structure accordingto claim 1, comprising the below layer structure following to the layerD): E) optionally a second adaptation layer, and F) a secondcurrent-conducting layer composed of doped Si, doped GaP or doped(AlGa)P.
 3. A semiconductor structure according to claim 1 or 2, whereinthe layer B) is p-doped or n-doped.
 4. A semiconductor structureaccording to one of claims 1 to 3, wherein y=1 to 30 mole-%.
 5. Asemiconductor structure according to one of claims 1 to 4, wherein c=1to 32.0 mole-%.
 6. A semiconductor structure according to one of claims1 to 5, wherein the semiconductor is a direct semiconductor.
 7. Asemiconductor structure according to one of claims 2 to 6, wherein thelayer F) is p-doped, if the layer B) is n-doped, and wherein the layerF) is n-doped, if the layer B) is p-doped.
 8. A semiconductor structureaccording to one of claims 1 to 7, wherein the optically active elementhas a layer structure (D1-D2-D3)_(n), wherein the layer D2 is a quantumwell layer of the said semiconductor, wherein the layers D1 and D3 arebarrier layers, and wherein n=1-50, in particular 1-15.
 9. Asemiconductor structure according to claim 8, wherein following one ofthe terminal layers D1 or D3, a barrier layer D4 is provided.
 10. Asemiconductor structure according to claim 8 or 9, wherein the barrierlayers are semiconductors having the compositionGa_(p)In_(q)N_(r)—P_(s)As_(t), wherein p=85-100 mole-%, q=0-15 mole-%,r=0-15 mole-%, s=60-100 mole-% and t=0-40 mole-%, wherein the total of pand q is always 100 mole-%, wherein the total of r, s and t is always100 mole-%, wherein the ratio of the totals of p and q on the one handand of r to t on the other hand is substantially 1:1, and wherein thebarrier layer has a layer thickness of preferably 5-50 nm
 11. Asemiconductor structure according to one of claims 1 to 10, wherein thefirst and/or the second adaptation layers are semiconductors having thecomposition Ga_(p)In_(q)N_(r)P_(s)As_(t), wherein p=90-100 mole-%,q=0-10 mole-%, r=0-10 mole-%, s=70-100 mole-% and t=0-30 mole-%, whereinthe total of p and q is always 100 mole-%, wherein the total of r, s andt is always 100 mole-%, and wherein the ratio of the totals of p and qon the one hand and of r to t on the other hand is substantially 1:1,and wherein the adaptation layer has a layer thickness of preferably50-500 nm.
 12. A semiconductor structure according to one of claims 1 to11, wherein a current-conducting layer and/or barrier layer disposedbetween the carrier layer and the optically active element is at thesame time an adaptation layer.
 13. A semiconductor structure accordingto one of claims 1 to 12, wherein underneath and/or above the opticallyactive element, at least one optical waveguide layer is provided, whichis optically coupled to the optically active element.
 14. Asemiconductor structure according to one of claims 1 to 13, whereinbetween the layers A) and D) and/or outside the layer F), there isprovided at least one periodic reflection structure.
 15. A semiconductorstructure according to one of claims 1 to 14, wherein the opticallyactive element has a fundamental emission wavelength in the range of700-1,100 nm.
 16. A method for the production of a monolithic integratedsemiconductor structure according to one of claims 8 to 15, wherein on acarrier layer A on the basis of doped or undoped Si or GaP, optionally afirst current-conducting layer B consisting of doped Si, doped GaP ordoped (AlGa)P is epitaxially grown, optionally a first adaptation layerC is epitaxially grown, and a multi-layer structure D, which forms anoptically active element including a semiconductor layer comprising asemiconductor according to one of claims 1 to 6, is epitaxially grown.17. A method according to claim 16, wherein on the optically activeelement optionally a second adaptation layer E is epitaxially grown, andon the optically active element or the second adaptation layer a secondcurrent-conducting layer F consisting of doped Si or doped GaP or doped(AlGa)P is epitaxially grown.
 18. A method according to claim 16 or 17,wherein the layer B is p-doped or n-doped.
 19. A method according toclaim 18, wherein the layer F) is p-doped, if the layer B) is n-doped,and wherein the layer F) is n-doped, if the layer B) is p-doped.
 20. Amethod according to one of claims 16 to 19, wherein the optical elementis formed by epitaxial growth of layers D1, D2 and D3, wherein the orderof the epitaxial steps is performed such that the layer structure is(D1-D2-D3)_(n), wherein the layer D2 is a quantum well layer of asemiconductor according to one of claims 1 to 4, wherein the layers D1and D3 are barrier layers, and wherein n=1-50, in particular 1-15.
 21. Amethod according to claim 20, wherein following one of the terminallayers D1 or D3, a barrier layer D4 is epitaxially grown.
 22. A methodaccording to claim 20 or 21, wherein the barrier layers aresemiconductors having the composition Ga_(p)In_(q)N_(r)P_(s)As_(t),wherein p=85-100 mole-%, q=0-15 mole-%, r=0-15 mole-%, s=60-100 mole-%and t=0-40 mole-%, wherein the total of p and q is always 100 mole-%,wherein the total of r, s and t is always 100 mole-%, wherein the ratioof the totals of p and q on the one hand and of r to t on the other handis substantially 1:1, and wherein the barrier layer has a layerthickness of preferably 5-50 nm.
 23. A method according to one of claims16 to 22, wherein the first and/or second adaptation layers aresemiconductors having the composition Ga_(p)In_(q)N_(r)P_(s)As_(t),wherein p=90-100 mole-%, q=0-10 mole-%, r=0-10 mole-%, s=70-100 mole-%and t=0-30 mole-%, wherein the total of p and q is always 100 mole-%,wherein the total of r, s and t is always 100 mole-%, wherein the ratioof the totals of p and q on the one hand and of r to t on the other handis substantially 1:1, and wherein the adaptation layer has a layerthickness of preferably 50-500 nm.
 24. A method according to one ofclaims 16 to 23, wherein a current-conducting layer and/or barrier layerdisposed between the carrier layer and the optically active element isat the same time an adaptation layer.
 25. A method according to one ofclaims 16 to 24, wherein underneath and/or above the optically activeelement, at least one optical waveguide layer is provided, which isoptically coupled to the optically active element.
 26. A methodaccording to one of claims 16 to 25, wherein between the layers A) andD) and/or outside the layer F), there is provided at least one periodicreflection structure.
 27. A method according to one of claims 16 to 26,wherein the optically active element has a fundamental emissionwavelength in the range of 700-1,100 nm.
 28. A III/V semiconductorhaving the composition Ga_(x)In_(y)N_(a)As_(b)P_(c)Sb_(d), whereinx=70-100 mole-%, y=0-30 mole-%, a=0.5-15 mole-%, b=67.5-99.5 mole-%,c=0-39.5 mole-% and d=0-15 mole-%, wherein the total of x and y isalways 100 mole-%, wherein the total of a, b, c and d is always 100mole-%, and wherein the ratio of the totals of x and y on the one handand of a to d on the other hand is substantially 1:1.
 29. A III/Vsemiconductor according to claim 28, wherein y=1 to 30 mole-%.
 30. AIII/V semiconductor according to claim 28 or 29, wherein c=1-32.0mole-%.
 31. A III/V semiconductor according to one of claims 28 to 30,wherein the semiconductor is a direct semiconductor.
 32. A semiconductorlayer comprising a semiconductor according to one of claims 28 to 31,wherein the layer thickness of the semiconductor layer is in the rangefrom 1-50 nm, preferably 2-20 nm.
 33. The use of a semiconductoraccording to one of claims 28 to 31 or of a semiconductor layeraccording to claim 32 for the production of a luminescence diode, aVCSEL laser diode, a VECSEL laser diode, a modulator structure or adetector structure.
 34. A method for the production of a semiconductorlayer according to claim 33 comprising the following steps: a substrateon the basis of doped or undoped Si or GaP is brought into a MOVPEapparatus, optionally a surface of the substrate is provided in at leastone epitaxial coating step first with respectively at least oneadaptation layer, one barrier layer, one current-conducting layer, onewaveguide layer and/or one reflection structure, an inert carrier gas isloaded with educts in defined concentrations, the loaded carrier gas isconducted over the surface of the substrate heated to a temperature inthe range of 300° C. to 700° C. or on the surface of the uppermost layeron the substrate for a defined duration of exposure, and the totalconcentration of the educts and the duration of exposure are adjusted toeach other such that the semiconductor layer is epitaxially formed witha given layer thickness on the surface of the substrate or on thesurface of the uppermost layer on the substrate.
 35. A method accordingto claim 34, wherein the following educts are used: C1-C5trialkylgallium, in particular triethylgallium (Ga(C₂H₅)₃) and/ortrimethylgallium (Ga(CH₃)₃), as a Ga educt, optionally C1-C5trialkylindium, in particular trimethylindium (In(CH₃)₃), as an Ineduct, ammonia (NH₃), mono(C1-C8)alkylhydrazine, in particulartertiarybutylhydrazine (t-(C₄H₉)—NH—NH₂), and/or1,1-di(C1-C5)alkylhydrazine, in particular 1,1-dimethylhydrazine((CH₃)₂—N—NH₂), as an N educt, arsine (AsH₃) and/or C1-C5 alkylarsine,in particular tertiarybutylarsine (t-(C₄H₉)—AsH₂), as an As educt,phosphine (PH₃) and/or C1-C5 alkylphosphine, in particulartertiarybutylphosphine (t-(C₄H₉)—PH₂), as a P educt, and optionallyC1-C5 trialkylantimony, in particular trimethylantimony (Sb(C₂H₅)₃)and/or triethylantimony (Sb(CH₃)₃), as an Sb educt, wherein the C3-C5alkyl groups may be linear or branched.
 36. A method according to claim35, wherein the educts are employed in the following molar ratios: Aseduct/group III educts 5-300, P educt/group-III educts 0-500, N educt/Aseduct 0.1-10, optionally Sb educt/As educt 0-1, wherein the surfacetemperature of the substrate is adjusted to the range from 500° C. to630° C., wherein the total pressure of carrier gas and educts isadjusted to the range from 10 to 200 hPa, wherein the ratio of the totalof the partial pressures of the educts to the partial pressure of thecarrier gas is between 0.005 and 0.1, and wherein the deposition rate is0.1 to 10 μm/h.
 37. A semiconductor layer obtainable with a methodaccording to one of claims 34 to
 36. 38. An integrated monolithicsemiconductor structure obtainable with a method according to one ofclaims 16 to 26.